Method and apparatus for identifying integrated circuits

ABSTRACT

An integrated circuit and method for identifying same is described. The integrated circuit includes a programmable identification circuit for storing electronic identification information. The integrated circuit also includes an optical identification mark displaying a machine-readable optical identification code which corresponds with the electronic identification information stored in the identification circuit. The data encoded in the optical identification code may be identical with that of the electronic identification information. Alternatively, a look-up table or other correlating means may be employed to associate the optical identification code with the electronic identification information. The integrated circuit is packaged in a housing, and another optical identification mark is placed on an external surface of the housing. This second optical identification mark displays a machine-readable optical identification code which is identical or correlated to the electronic identification information stored in the identification circuit and/or the optical identification code displayed by the optical identification mark on the integrated circuit. Consequently, convenient and traceable identification of individual integrated circuits is provided during and after manufacture.

TECHNICAL FIELD

This invention relates generally to integrated circuits, and moreparticularly to identification information for integrated circuits.

BACKGROUND OF THE INVENTION

Typically, many identical integrated circuits are constructed on asingle wafer of semiconductor material, such as monocrystalline siliconor gallium arsenide. The portion of the wafer occupied by a single oneof the integrated circuits is called a die. After completed fabricationof the integrated circuits, a series of tests (known as Probe) isperformed in which the function of each die is tested. The test datacollected for each die is used in subsequent assembly/packaging steps toensure that only properly functioning die are packaged as integratedcircuit chips.

Following the Probe test, the individual dies are separated from oneanother, and each properly functioning die is encapsulated (usually inplastic or ceramic) in a package having electric leads to form anintegrated circuit chip. Subsequently, a series of testing operations isperformed for each of the integrated circuit chips, with test datacollected for each of the chips.

In order to properly correlate the various test results with theappropriate die or dies, accurate identification of each of the dies isrequired, both before and after packaging as an integrated circuit chip.The ability to identify particular dies can also be important followingcompleted manufacture of the integrated circuit chip. For example, whenan integrated circuit chip unexpectedly fails during later use, themanufacturer of the chip may wish to identify other potentially failingchips and the users of those chips.

Many of today's integrated circuits provide electronically readableidentification information which is programmed into the integratedcircuit itself—usually during Probe testing. Also, chip packages usuallyhave an ink or laser-scribed mark which provides some usefulinformation, such as date and country of manufacture, product andpackage types, speed and other test parameters, and manufacturing lotidentification. However, information uniquely identifying the particularintegrated circuit within a chip is included only in the electronicallyreadable identification information.

The electronically readable identification information is usuallyavailable only during those manufacturing procedures in which theintegrated circuit is electrically tested. Also, retrieving theelectronically readable identification information is usually done witha relatively sophisticated semiconductor testing apparatus, whichnecessarily makes physical contact with the integrated circuit chip inorder to access the identifying information. There exist a number ofmanufacturing process steps during which such physical contact does notoccur, and hence traceable identification of the individual integratedcircuit chips through the various manufacturing processes is quitedifficult. Also, once the manufacturer ships the integrated circuit chipto a customer, the unique identification information is not readilyavailable.

SUMMARY OF THE INVENTION

A method of identifying an integrated circuit is provided in which theintegrated circuit is both programmed with electronic identificationinformation and marked with a corresponding machine-readable opticalidentification code. The integrated circuit may be marked with anadhesive label, inscribed with a laser, or marked in any of a variety ofsuitable ways of displaying machine-readable optical identificationcodes. The integrated circuit may include a plurality of programmablelinks which are programmed to store the electronic identificationinformation, or include any of a variety of suitable adapted circuitsfor non-volatile data storage.

The method further includes the steps of reading the opticalidentification code and associating it with the corresponding electronicidentification information. A look-up table or other suitablecorrelating means may be used for performing the association step.Alternatively, the optical identification code may encode exactly thesame data values as the electronic identification information.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram depicting an integrated circuit which includesan identification circuit and a machine-readable optical mark.

FIG. 2 depicts a semiconductor wafer including a plurality of dies, eachof which has a machine-readable optical mark.

FIG. 3 depicts a packaged integrated circuit chip which has amachine-readable optical mark.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, certain specific details are set forth inorder to provide a thorough understanding of embodiments of the presentinvention. It will be clear, however, to one skilled in the art that thepresent invention may be practiced without these details. In otherinstances, well-known circuits and structures have not been shown indetail in order not to unnecessarily obscure the description of theembodiments of the invention.

FIG. 1 depicts an integrated circuit 10, which may be any of a widevariety of integrated circuits fabricated by conventional or newlydeveloped methods. The integrated circuit 10 includes a programmableidentification circuit 12 having a bank of programmable links 13, forstoring electronic identification information uniquely identifying theintegrated circuit. The identification circuit 12 can be any of avariety of circuits suitable for such purpose, whether currently wellknown or subsequently developed. The programmable links can be fuses,antifuses, or any of a wide variety of circuit elements suitable fornon-volatile data storage, whether currently well known or subsequentlydeveloped. The method by which the identification circuit 12 isprogrammed to store the electronic identification information, as wellas the method by which such information is retrieved from theidentification circuit, can be any of a wide variety of methods for suchpurpose, whether currently well known or subsequently developed. Forexample, U.S. Pat. No. 5,301,143 to Ohri et al., which is incorporatedherein by reference, describes an example programmable identificationcircuit 12 and methods for storing/retrieving information to/from same.

The integrated circuit 10 also includes a machine-readable opticalidentification mark 14. The identification mark 14 may be an adhesivelabel, a laser-scribed mark, or any of a wide variety of suitable marks.The identification mark 14 displays an optical identification code 15which corresponds with the electronic identification information storedin the programmable identification circuit 12. The opticalidentification code 15 can be any of a wide variety of machine-readableoptical identification codes, whether currently well known orsubsequently developed. The optical identification code 15 can be readby any of a wide variety of methods and with corresponding ones of awide variety of optical code readers, whether currently well known orsubsequently developed. For example, a particular optical identificationcode and a method and apparatus for reading and decoding the code aredescribed in U.S. Pat. No. 5,389,770 to Ackley, which is incorporatedherein by reference.

FIG. 2 depicts a semiconductor wafer 16 on which a plurality ofintegrated circuits 10 have been constructed, each on a correspondingone of a plurality of semiconductor dies 18. On each of the dies 18 is acorresponding one of a plurality of the optical identification marks14A, each having an optical identification code 15A which correspondswith the electronic identification information stored within theidentification circuit 12 (see FIG. 1). FIG. 3 depicts a packagedintegrated circuit chip 20, within which one of the dies 18 (see FIG. 2)is encapsulated. The integrated circuit 10 (see FIGS. 1 and 2) iselectrically accessible via a plurality of electric leads 22. An outersurface of the packaged chip 20 is marked with an optical identificationmark 14B having an optical identification code 15B which correspondswith the electronic identification information stored within theidentification circuit 12 (see FIG. 1). Note that distinct referencenumerals are used to identify the optical identification marks and codesin FIGS. 1-3, indicating that various non-identical identification marksand codes may be used at different stages of the manufacturing process.

Typically, the electronic identification information is programmed intothe identification circuit 12 during. Probe testing of the various dies18 included in the wafer 16. One or more of the identification marks14-14B could then be produced to include an optical identification codewhich encodes data that is identical to the data stored in theidentification circuit 12. In other words, the electronically accessiblepattern of 1's and 0's stored in the identification circuit 12 is thesame as the optically accessible pattern of 1's and 0's encoded in oneor more of the identification marks 14-14B. Alternatively, one or moreof the identification marks 14-14B can be correlated, via a look-uptable or other conventional correlation means, with the particularelectronic identification data stored in the identification circuit 12—amore flexible approach then requiring identical data.

Those skilled in the art will appreciate a number of advantages achievedby the above-described embodiments of the present invention.Conventionally, integrated circuits have included only theelectronically accessible identification information, as well as visualmarking information intended for human eyes. Thus accurateidentification of individual integrated circuits has been available onlyduring manufacturing processes in which the integrated circuit iselectrically accessed. In contrast, the present invention providesidentification marks having an optical identification code associatedwith the electronic identification information, thereby providingconvenient, accurate and traceable identification of individualintegrated circuits during and following the manufacturing process.Also, the ability to optically identify the integrated circuit avoidsthe need for physical contact, thereby minimizing the possibility ofdamage to the integrated circuit by the act of electronically readingthe identification data—a common concern with current technology.

As stated above, the optical identification marks 14-14B can be any of awide variety of such marks, and the method and apparatus for encodingoptical identification information and reading such information can beany of a wide variety of suitable ones for such purpose. Similarly, theidentification circuit 12 can be any of a wide variety of suitablyadapted circuits, and the particular methods for programming andretrieving electronic identification information thereto and therefromcan be any of a wide variety of suitably adapted methods. It is thecombination of both electrically accessible identification informationand associated machine-readable optical identification codes whichprovides traceability of the identification optical through themanufacturing process, as well as after it has been shipped to acustomer.

While certain embodiments of the invention have been described forpurposes of illustration, various modifications may be made withoutdeviating from the spirit and scope of the invention. Numerousvariations are well within the scope of this invention, and accordingly,the invention is not limited except by the appended claims.

1. A method of identifying a plurality of substantially identicalintegrated circuits formed on a common substrate, comprising the stepsof: programming each of the integrated circuits with respectiveelectronic identification information distinguishing the integratedcircuits from one another; and marking each of the integrated circuitswith respective optical identification code which corresponds with therespective electronic identification information; reading the opticalidentification code on each of the integrated circuits; and accessing alookup table to associate the optical identification code on each of theintegrated circuits with the corresponding electronic identificationinformation.
 2. The method of claim 1 wherein the step of programmingeach of the integrated circuits with electronic identificationinformation includes the step of programming one of a plurality ofprogrammable links.
 3. The method of claim 1 wherein the step of markingeach of the integrated circuits with optical identification codeincludes the step of placing an adhesive label on each of the integratedcircuits.
 4. The method of claim 1 wherein the step of marking each ofthe integrated circuits with optical identification code includes thestep of inscribing a symbol on each of the integrated circuits.
 5. Themethod of claim 1 wherein the step of marking each of the integratedcircuits includes the step of marking respective portions of thesubstrate on which the integrated circuits are formed.
 6. In a pluralityof substantially identical integrated circuits formed on a commonsubstrate, each of the integrated circuits including a programmablecircuit for storing respective electronically readable identificationcode which distinguishes the integrated circuits from one another, amethod of identifying the integrated circuits, comprising the steps of:marking each of the integrated circuits with respective opticalidentification code; accessing a lookup table to associate the opticalidentification code on each of the integrated circuits with therespective electronically readable identification code and reading theoptical identification code on each of the integrated circuits.
 7. Themethod of claim 6 wherein the step of associating the opticalidentification code on each of the integrated circuits with therespective electronically readable identification code includes thesteps of: reading the electronically readable identification code storedin each of the integrated circuits; reading the optical identificationcode marked on each of the integrated circuits; and correlating the readelectronically readable identification code with the read opticalidentification code for each of the integrated circuits.
 8. The methodof claim 6 wherein the step of associating the optical identificationcode on each of the integrated circuits with the respectiveelectronically readable identification code includes the step ofencoding identical data in the optical and electronically readableidentification codes.
 9. The method of claim 6 wherein the step ofmarking each of the integrated circuits includes the step of markingrespective portions of the substrate on which the integrated circuitsare formed.
 10. A wafer comprising a plurality of dies, each dieincluding an integrated circuit having a programmable identificationcircuit that stores identification data, and each die having an opticalidentification mark positioned thereon and encoding informationcorresponding to the identification data, optical identification mark oneach die being accessed through a lookup table to correspond to theelectronic identification information.
 11. The wafer of claim 10 whereinthe programmable identification circuit includes a plurality ofprogrammable links.
 12. The wafer of claim 10 wherein the opticalidentification mark encodes information identical to the identificationdata.
 13. The wafer of claim 10 wherein the identification data uniquelydistinguishes each of the dies.
 14. A plurality of integrated circuitchips, each comprising: a housing; an integrated circuit enclosed withinthe housing and including an identification circuit that storesidentification data distinguishing each of the integrated circuit chipsfrom one another; and an optical mark positioned on an exterior surfaceof the housing and encoding identification information being accessedthrough a lookup table to correspond to the identification data.
 15. Theintegrated circuit chips of claim 14, further comprising electricalcontacts connected to said housing and adapted to provide electricalconnection between the integrated circuit and circuitry external to thehousing.
 16. The integrated circuit chips of claim 14 wherein theoptical mark is a first optical mark encoding first identificationinformation, and further comprising a second optical mark positioned onthe integrated circuit enclosed within the housing and encoding secondidentification information corresponding to the identification data. 17.The integrated circuit chips of claim 16 wherein the firstidentification information is identical to the second identificationinformation.
 18. The integrated circuit chips of claim 14 wherein theidentification information is the same as the identification data.
 19. Amethod of identifying a plurality of substantially identical integratedcircuits formed on a common substrate, each of the integrated circuitsbeing formed on a respective one of a plurality of substrate dies, themethod comprising: programming each of the plurality of integratedcircuits with respective electronic identification information for eachof the integrated circuits; and marking each of the dies with opticalidentification code which corresponds with the respective electronicidentification information; reading the optical identification code oneach of the integrated circuits; reading the electronic identificationinformation from each of the integrated circuits; and accessing a lookuptable to associate the optical identification code on each of theintegrated circuits with the corresponding electronic identificationinformation.
 20. The method of claim 19 wherein the electronicidentification information is distinct for each of the integratedcircuits.
 21. The method of claim 19 wherein the optical identificationcode is distinct for each of the dies.
 22. The method of claim 19wherein the optical identification code and the electronicidentification information include identical data.
 23. A method ofidentifying an integrated circuit, comprising: programming theintegrated circuit with an electronic identification information;marking the integrated circuit with an optical identification code thatcorresponds with the electronic identification information; reading theelectronic identification information; and associating the opticalidentification code with the read electronic identification informationthrough a correlation mechanism.
 24. The method of claim 23 wherein theact of programming the integrated circuit with electronic identificationinformation comprises programming at least one of a plurality ofprogrammable links.
 25. The method of claim 23 wherein the act ofmarking the integrated circuit with an optical identification codeincludes the step of placing an adhesive label on the integratedcircuit.
 26. The method of claim 23 wherein the correlation mechanismcomprises accessing a correlation instrument.
 27. The method of claim 26wherein the correlation instrument comprises a lookup table.
 28. Themethod of claim 26 wherein the correlation instrument contains theoptical identification code and the electronic identificationinformation for associating the optical identification code with theelectronic identification information.
 29. A method of identifying anintegrated circuit, comprising: programming the integrated circuit withan electronic identification information; marking the integrated circuitwith an optical identification code that corresponds with the electronicidentification information; reading the electronic identificationinformation; and cross-referencing the optical identification code withthe read electronic identification information by utilizing acorrelation instrument.
 30. The method of claim 29 wherein the act ofprogramming the integrated circuit with electronic identificationinformation comprises programming at least one of a plurality ofprogrammable links.
 31. The method of claim 29 wherein the act ofmarking the integrated circuit with an optical identification codeincludes the step of placing an adhesive label on the integratedcircuit.
 32. The method of claim 29 wherein the correlation instrumentcomprises a lookup table.
 33. The method of claim 29 wherein thecorrelation instrument contains the optical identification code and theelectronic identification information for cross-referencing the opticalidentification code and the electronic identification information.